Fuse link



L... P. BOLL FUSE LTNKV Filed may 19, 195o March 24, 1931.

Patented Mar. 24, 1931 UNITED STATES PATENT OFFICE LESTER PIERCE BOLL, KOF" UNIVERSITY CITY, MISSOURI, ASSIGNOR TO W. N. MAT- THEWS CORPORATION, OF ST. LOUIS, MISSOURI, A CORPORATION OF MISSOURI FUSE Application led May 19,

This invention relates to fuse links, and with regard to certain more specific features, to a new and improved fuse link for use in expulsion types of fuse cartridges. Among theseveral objects of the invention maybe noted the provision of a fuse link wherein a combination of a weight and a spring insures a quick opening of the circuit `under all conditions of overload; the

Vprovision of a fuse link which, although new,

may be used with older types `of fuse cartridges, thereby preventing equipment already installed from becoming obsolete; the provision of a fuselink which gives a positive indication when the fuse is blown; the provision of a fuse which advantageously uses expulsion gases engendered when a fuse is blown by short circuiting, but which does not depend only upon these engendered gases for a quick break; and the provision of a fuse link which is simple, economical. and easily manufactured and installed. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts whichv will be exemplified in the structure hereinafter described, and the scope. of the application of which will be indicated in the following claims.

In the accompanying drawings, in which is illustrated one of various possible embodiments of the invention,

Fig. 1 is a typical installation of an expulsiony type of fuse wherein the new and improved fuse link is employed;

Fig. 2 is a longitudinal cross section of a typical fuse cartridge wherein the new and improved fuse link is connected; and,

Fig. 3 is an elevation of the new and im'- proved fuse link.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

, .Referring now more particularly to Fig 1, there is illustrated at numeral 1 a supporting bracket to which are attached by means of shackle bolts 5 insulators 3. The insulators 5 support arms? which have bolted LINK 1930. Serial No. 453,818.

thereto pairs of `terminal spring clips 9. These clips are of a class which engage two sides of a connecting member by means of a plurality of spring engaging fingers.

Bolted between each arm 7 and its respective set of clips 9 is a terminal piece 11 to which may be connected leads 13.

Between the lowermost set of clips 9 and its respective arm 7 is held a hinge member 15. This hinge member 15 is provided with a flat portion 17 adapted to Hatly engage wih arm 7. The hinge also comprises. a pair of downwardly hooked arms 23 extending from said fiat portion.

The fuse cartridge 25 comprises a fuse link 27 which is adapted to electrically connect the spring terminal clips 9. This fuse is removably connected to an upper metallic block 29 which is provided with proper parallel faces 43 for engaging the upper resilient spring clips 9. A stud 31 removablv retains the fuse in position with said upper block 29. This block is also provided with a suitable bridge portion 33 which may be hooked by the end of a suitable insulating tool so that the operator may draw the block 29 from the upper clip 9 without physically engaging current carrying members. The upper metallic block 29 is held to the insulating cartridge tube 35 by means ot' a set screw 37. Y j

Toward the lower end of cartridge tube 35 there is held by means of a suitable set screw 39 a hollow terminal hnge block 41. This block 41 comprises a hollow form having substantially fiat parallel faces 43 for the purpose of engaging the lower resilient spring clips 9. `Grudgeons 45 sidew'ardlyj extend from these parallel faces for the purpose of hingedly engaging vthe hinge member 15 at the hook portion of the arms 23. On one face of the block 41 there is provided a tapped surface adapted to receive a set 'screw 47 for holding the lower end of fuse 27.

It is to be understood that the foregoing disclosure is exemplary only and is but an illustration ,of a typical installation which serves to show clearly the use of my invention. A more detailed descriptionof the switch hanger and fuse cartridge may be obtained by referring to United States Patent 1,704,961, issued to Theodore Birkenmaier, dated March 12, 1929.

The portion of the fuse link 27 which is adapted to be blown during overloads is preferably composed of two lengths of nichrome wire 49 and 51 soldered together as shown at numeral 53. The size of the nichrome wires 49 and 51, the amount and kind of solder used, and the overlap in making the joint 53 may so be adjusted and/or chosen that this portion of the fuse link will carry normal load currents without any appreciable heating and when a-n overload is encountered, the link will melt or blow at the joint 53. Nichrome wire possesses the special advantage that it does not stretch by heating and the desirability of this feature will be apparent hereinafter.

To the upper end of the fuse link there is soldered or otherwise affixed a lug v55 adaptedv to be compressingly held within the fuse cart-iv ridge25 by means of stud 31 (see Fig; 1).

To the lower end o-f the length 51 there is soldered or otherwise affixed a length of copper or other wire 57. This wire should be of such composition and size that it will not stretch during normal load currents.v For purposes of economy, this wire may conveniently be copper wire but should be of a larger cross-sectional area than the nichrome wires 49 and 51 so that it will carry lthe normal currents without any appreciable heating and/or stretching.

On wire 57 there is tightly aiiixed a weight 59. Weight 59 is preferably"` made of lead and preferably, though notnecessarily, bullet-shaped,` and should be small enough to easily move within cartridge tube 25 but 'should belarge enough in diameter to present an appreciable surface which will afford a driving action to the slug when gases are engendered by the fuse blowing under a heavy overload. l v

To theilower end of wire 57 there'is soldered or otherwise aiiixed a helical spring- 61. This spring 61 may conveniently be made of spring brass or phosphor bronze wire and should be so proportioned that it willY not heat and stretch appreciably under nor- It shouldfurthermore be so proportioned that the fuse link may be given an appreciable longitudinal stress when connected within fuse cartridges 25.

To the -lower end of spring 61 there is soldered or otherwise aiiixed a length of wire 63 which may be of the same composition and size as wire 57. The lower end of this wire 63, after making a hairpin turn at the bottom of the tube, engages with set screw 47 and y completes the circuit thereby/between the sets of clip`s-9 by means of fuse link 27.

When inserting this'fuse link within its cartridge, the upper terminal or lug 55 is .first secured in .place by means of stud 31. A tension is `then applied to the fuse link sol as to appreciablystretch the spring 61 (it is shown in a stretched position in Fig. 2) and with the spring in this stretched position the the component parts of the link.

Assuming first that the load current gradually increases to the blowout value, it is clear that when the joint 53 is melted and broken by this value of current, the spring 61 will quickly pull the adjoining ends of wires 49 and 51 apart and provide thereby a relatively quick and large opening for the break. The length of this break would, in the. absence of the slug or weight 59 not be appreciably greater than the distance which the spring 61 has been stretched at the time of installing the link. It will be seen however, that after the spring has pulled apart the joint 53, then the dead weight of the slug 59 and the kinetic energy imparted thereto by the spring 61 result in the initial gap being widened, the parts of the link below point 53 dropping entirely from the cartridge tube.

The weight in effect prevents the fuse linkfrom being supported in arcing position by the sides of the tube, said weight clearing the tube after'the spring has effecteda sudden break. f

It is clear that the provision of the weight in combination with the spring affords a longer break than would be provided by the spring alone. It is also lclear that a quicker break is provided than what would'be obv tained if the weight alone were used, especially on sofcalled dragging overloads.

For short circuits or sudden application of heavy overload, an even quicker break is effected. As has been pointed out hereinbefore, the weight 59 .is large enough in cross! sectional area to afford an appreciable surface against which press the gasesengendered by the sudden gasificationof the fuse, tlius discharging the weight from the end of the tube. It is to be understood that the upper end of the cartridge 'tube is closed tight and the lower end is open. Although this yexpulsive force exerted upon weight 59 by the engendered gases serves toprovideV a quick break, it is clear that this action is supplementary to the combined effect of the weight and the spring. Upon a sudden overload all lo three of* these causes contribute togimproved action; upon a dragging overload, the spring and the weight are effective.

It is thus seen `that a quick and -long break is effected under any condition of overload.' It is clear that the provision of such a long and quick break within a closed tube has distinct advantages. As has been pointed out, the enclosed cartridge tube in combination with a weight on a fuse link provides, beside the other advantages enumerated, an expulsive type of fuse especially efective'at short circuits or quick overloads. The enclosure for the fuse link also provides an element of safety not found in the open type of fuse.

As shown` the fuse is preferably mounted in an upright position. Mounted in such a position, the eHect of the spring and weight becomes more effective, as is also the action of the engendered gases, if\ any.

Inasmuch as the weight and spring hang out of the open end of the tube after the fuse has blown, there is provided avpositive indication that the fuse is blown. `With such fuses mounted at substantial heights, this is a distinct vadvantage because a lineman on the ground can easily determine which of a number f fuses is blown before climbing up to insertnew fuse links.

By the term soldered joint is meant herein, one which effects a juncture between different pieces by an applied melted material which subsequently hardens.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in carrying out the above constructions without departingfrom the scope of the invention, it is intended that all matter contained in the above descr-ipion or shown in the accompanying drawings shall be interpreted as illustrative and not in a'limiting sense.

I claim:

1. A fuse link comprising lengths of wire, a joint connecting said lengths, a weight on one of said lengths, and a lspring in said length containing said weight, said link be` ing adapted to melt at said soldered joint upon overload.

2. A fuse link comprising lengths of wire, a joint connecting saidl lengths, a weight on one of said lengths, and a spring in said length containingsaid weight, said joint being positioned above the weight and the spring. i p f 3. In a fuse cartridge means for quickly providinga long break comprising a weight, a spring vand 'a length of wire having 'a 'fusible point, said weight and said spring being adaptedto be expelled from said fuse cartridge when saidjoint is blown.

4. A fuse link comprising lengths of wire,

ajoint connecting said lengths, a weight on one of said lengths, and a spring in said length containing said weight.

5. In a fuse cartridge, a fuse link comprising lengths of wire, a soldered joint connecting said lengths, a weight on one of said lengths, a spring in said length containing said weight, said link being adapted to be held within said cartridge in a strained condition and adapted to move out of said cartridge when said link blows.

6. In a fuse cartridge, a fuse link comprising lengths of wire, a soldered joint connecting said lengths, a weight on one of said lengths, a spring in said length containing lsaid weight, said weight having an areay adapted to offer appreciable resistance to engendered gases when said fuse blows suddenly, said gases expelling said weight from said cartridge. i

7. A fuse link comprising a length of wire, a calibrated fusible portion therein, a weight on said link, a spring inserted in said link,

said spring being adapted to permit of the tensioning of said link when inuse and adapted to impart movement to said weight when said fusible portion blows.

8. In a fuse switch, means for providing a lquick and long break under all conditions of overload, comprising a fuse cartridge closed at one end and openl at the other, said cartridge containing a tensioned and weighted fuse link.

9. In a fuse cartridge, afuse link compris- A ing lengths of wire, a soldered joint connecting said lengths, a weight on one of said lengths, a spring in said length containing said weight, said link being adapted to be held within said cartridge in a strained condition and adapted to move out of said lcartridge when said link blows, the spring causing sudden initial movement to form an incipient gap, said weight continuing said movement 'to widen they gap.

. l0. A switch cartridge comprising a tube having a lower opening and closed top, ay

fuse link therein connected at the top and outside of said lower opening and having a hairpin turn at said lower opening, a meltable l portion in said link near said top and a strained spring and a yweight associated withv saidv link between the meltable portion and said lower openings ,c Y

11. A switch cartridge comprising a tube having a lower opening and closed top,al fuse `link therein connected at the top and having fastening said link outside of said opening and a meltable portion in said link near said top and a strained spring and a weight asso-l ciated with said link between the meltable portion and said lower fastening means.

13. In a fuse a fuse link, means for uprightly placing said link, an upper meltable portion in said link and a strained spring and weight connected therewith below the meltable portion.

14. In a fuse a fuse link, means for uprightly placing said link, an upper meltable por-A tion in said link and a strained spring and weight connected therewith below the meltable portion, said spring being below the weight.

' l5. In a fuse a fuse link, means for uprightly placing said link, an upper meltable portion in said link and a strained spring and weight connected therewith below the meltable portion said spring being below the weight and a tube surrounding those portions of the link carrying the meltable portion,

weight and spring. I

In testimony whereof, I have signed my name to' this specification this 16th day of May, 1930.

` LESTER PIERCE BOLL. 

